JPH0622175A - Noise eliminating circuit - Google Patents

Abstract

PURPOSE:To eliminate the noise of a video signal in response to a noise level by detecting noise in the noise component in a non-signal block for a vertical synchronizing signal period and integrating the noise level by an integration circuit. CONSTITUTION:An input signal 102 is inputted to a synchronizing signal generating circuit 2, a timing signal 103 of a non-signal part is generated, a sampling circuit 3 extracts a vertical synchronizing signal missing part from the signal 102 based on the signal 103. An integration circuit 4 integrates a non-signal part of the vertical synchronizing signal and a coefficient generating circuit 5 outputs a noise level 104. On the other hand, the signal 102 is given to a Y/C separation circuit 6, from which a luminance signal 105 is outputted. A BPF 7 extracts a high frequency component 106 having the noise component. A nonlinear processing circuit 9 processes the signal 105 and inputs a nonlinear processing signal 107 to a subtractor circuit 10 and a noise elimination output signal 108 is obtained via the subtraction of the signal 107 from the signal 105.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise eliminating circuit,
In particular, the present invention relates to a noise removing circuit used for removing a noise component of a video signal in a video signal processing device such as a television receiver or a VTR.

[0002]

2. Description of the Related Art Conventionally, in TVs and VTRs,
As circuits for removing a noise component from a video signal, there are two known circuits, Japanese Patent Laid-Open No. 3-132268 and Japanese Patent Laid-Open No. 21780.

As a first conventional technique, Japanese Patent Laid-Open No. 3-132
The outline of 268 will be described with reference to FIG. In FIG. 3, the video signal 118 is input to the noise detection circuit 22 and the video signal processing circuit 25, respectively. Noise detection circuit 2
In 2, the microcomputer (hereinafter, referred to as CPU) 24 is supplied with the vertical synchronization period sampling pulse 119, and detects and outputs a noise component included in the vertical synchronization period. This noise detection signal is sent to the A / D conversion circuit 2
It is converted into a digital signal by 3 and input to the CPU 24. Through this digital signal, the CPU 24 discriminates whether the noise component level is large, medium, or small. Depending on the discriminant value of this noise component level, the CP
From U24, each signal of the sharpness control 120, the color control 121, and the NR control 122 is output and sent to the video signal processing circuit 25.
By varying the noise removal level in the video signal processing circuit, noise removal according to the noise level is performed. The noise-removed signal output from the video signal processing circuit 25 is input to the CRT 26 and displayed.

Next, as a second conventional technique, Japanese Unexamined Patent Publication No.
The outline of 21780 will be described with reference to FIG. The video signal 123 is input to the Y / C separation circuit 27 and divided into a luminance signal 124 and a color signal 125. These divided signals are converted into digital signals by A / D converters 28 and 29, respectively, and input to the Y / C mixer 30. These digital signals are mixed in the Y / C mixer 30 so as to be a serial output, such as a luminance signal for a certain time, a color signal for the next time, and a luminance signal for the next time by time division. It The mixed output signal is input to the subtraction circuits 31 and 32, and the field difference signal of the mixed output signal, that is, the noise component is detected via the field memory 34 and the subtraction circuit 32. By the detected noise component, the non-linear processing circuit 35 for the luminance signal and the non-linear processing circuit 3 for the color signal
The 6 non-linear characteristics are set separately. The output signal of the non-linear processing circuit 35 for the luminance signal and the output signal of the non-linear processing circuit 36 for the chrominance signal are output from the Y / C mixer 30 via the switch 37 which is switch-controlled by the timing generator 33. In the case of the luminance signal, the output signal of the non-linear processing circuit 35 for the luminance signal corresponds, and in the case of the color signal,
Switching control is performed so that the output signals of the non-linear processing circuit 36 for color signals correspond. The signals that are switched by the switch 37 and output to each of them are subjected to noise reduction of the luminance signal and the chrominance signal through the subtraction operation of the subtraction circuit 31.

[0005]

In the above-mentioned conventional noise removing circuit, since the integrating action corresponding to the noise level is not performed, the noise removing circuit operates even for sudden noise, Since the noise removal level changes frequently, there is a drawback in that the image screen feels strange. Further, in the conventional noise removal circuit shown in FIG. 4, since the noise component is detected by the field difference, it is difficult to remove the noise of the video signal in a moving image in which a field difference signal other than noise is generated. There is a drawback.

[0006]

A noise removing circuit according to a first aspect of the present invention inputs an A / D converter for converting a video signal into a digital signal, and a digital video signal output from the A / D converter. , A sync signal generating circuit for extracting and outputting a timing signal of a no-signal portion in the vertical synchronizing signal, and sampling for extracting and outputting noise of a no-vertical synchronizing signal from the digital video signal via the timing signal A circuit, an integrating circuit that integrates and outputs noise of the vertical synchronization no-signal portion extracted by the sampling circuit, and an integrated signal of noise output from the integrating circuit is input, and a noise level value corresponding to the noise A coefficient generation circuit for setting and outputting and a luminance signal for inputting the digital video signal and separating a luminance signal from the digital video signal for output. A separation circuit, a high-frequency component detection circuit that inputs the luminance signal, extracts a high-frequency component including a noise component in the luminance signal, and outputs the high-frequency component, and is preset for non-linear processing with respect to a noise level value. Corresponding to the noise level value input from the coefficient generation circuit and a storage circuit that stores a plurality of patterns of non-linear waveforms, the pattern of the non-linear waveform in the storage circuit is appropriately selected, and the selected non-linear waveform is used. A non-linear processing circuit that performs non-linear processing on a signal including a high-frequency component output from the high-frequency component detection circuit; and a non-linear output from the non-linear processing circuit based on a luminance signal output from the luminance signal separation circuit. A subtraction circuit for subtracting the processed signal,
Is provided at least.

The noise removing circuit of the second invention inputs an A / D converter for converting a video signal into a digital signal and a digital video signal output from the A / D converter, and outputs the digital video signal. A 1-frame memory for delaying a signal by 1 frame and outputting the signal; a differential circuit for subtracting the digital video signal output from the 1-frame memory from the digital video signal to output a differential signal; and the A / D converter. A sync signal generating circuit for inputting a digital video signal output from the vertical sync signal and extracting and outputting a timing signal of a no-signal part in the vertical sync signal; and a vertical sync no-signal part from the difference signal via the timing signal. Sampling circuit that extracts and outputs the noise of, and the noise of the vertical synchronization non-signal portion extracted by the sampling circuit is input A coefficient generation circuit that sets and outputs a noise level value corresponding to the noise, a luminance signal separation circuit that inputs the digital video signal, separates a luminance signal from the digital video signal, and outputs the luminance signal, and a luminance signal separation circuit that outputs the luminance signal. A high-frequency component detection circuit that inputs, extracts and outputs a high-frequency component including a noise component in the luminance signal,
A storage circuit that stores a plurality of patterns of non-linear waveforms that are preset for non-linear processing on the noise level value, and a non-linear waveform pattern of the storage circuit that corresponds to the noise level value input from the coefficient generation circuit. A non-linear processing circuit that appropriately selects and performs non-linear processing on a signal including a high frequency component output from the high frequency component detection circuit according to the selected non-linear waveform, and a luminance signal output from the luminance signal separation circuit Accordingly, at least a subtraction circuit for subtracting the non-linear processing signal output from the non-linear processing circuit is provided.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. As shown in FIG. 1, this embodiment is
/ D converter 1, synchronization signal generating circuit 2, sampling circuit 3, integrating circuit 4, coefficient generating circuit 5, Y / C separation circuit 6, and bandpass filter (hereinafter referred to as BPF) 7
A ROM 8, a non-linear processing circuit 9, and a subtraction circuit 10. In this embodiment, in particular, an integrating circuit 4 is added to the conventional circuit of FIG. 3, a coefficient generating circuit 5 is provided in place of the sampling circuit 3 and the CPU 24, and a linear waveform of a three-stage nonlinear circuit is used as a noise removing circuit. The built-in ROM 8 is provided, and the linear waveform of the non-linear circuit is selected by the coefficient generating circuit 5.

In FIG. 1, a video signal 101 is input to an A / D converter 1 and digitized input signal 10
It is output as 2. The input signal 102 is input to the sync signal generation circuit 2 and the timing signal 103 of the portion where the sync signal in the vertical sync signal does not change, that is, the non-signal portion.
(See FIG. 6B) is generated and output. With this timing signal 103, in the sampling circuit 3, the vertical synchronizing no-signal portion is extracted from the input signal 102 through the sampling action, and the integrating circuit 4 corresponding to the no-signal portion integrates the vertical synchronizing no-signal portion, The noise level value 104 is output by the coefficient generation circuit 5. The signal extracted by the sampling circuit 3 is
Since it is originally a signalless portion, only noise components are present.
From this, the noise level value 104 represents the noise level, and is, for example, a value such as "1", "2", "3" in ascending order of the noise level. Further, in the integrating circuit 4, integration is performed over several fields to several tens of fields in order to prevent malfunction due to sudden noise.

On the other hand, the input signal 102 is the input signal 1
02 is input to the Y / C separation circuit 6 for separating the luminance signal and the color signal, and the luminance signal 105 is output via the Y / C separation circuit 6. The brightness signal 105 is input to the BPF 7 and has a peak of 1.7 MHz as shown in FIG.
The PF 7 extracts the high frequency component 106 having a noise component. The ROM 8 stores two or more patterns of predetermined non-linear waveforms for non-linear processing. The waveform in the ROM 8 is selected as follows according to the value of the noise level value 104.

For example, in the case of a luminance signal with little noise such that the noise level value 104 is "1", FIG.
The non-linear waveform as shown in FIG.
To reduce. When the noise level value 104 is an intermediate noise level such as “2”, it is conventionally used,
A non-linear waveform as shown in FIG. 7B is selected. Further, for a luminance signal with a lot of noise such that the noise level value 104 is "3", a non-linear waveform that allows more high frequency components of the waveform as shown in FIG. 7C to be selected is selected. A luminance signal 1 is generated by the nonlinear processing circuit according to the selected waveforms.
05 is processed and output as the non-linear processed signal 107. Next, the non-linear processed signal 107 is input to the subtraction circuit 10, and the noise-removed output signal 108 is obtained through the subtraction action of the non-linear processed signal 107 on the luminance signal 105. In this way, the luminance signal with less noise is processed while leaving the high-frequency component, and the luminance signal with many noise is processed with the high-frequency component dropped. By doing this, the noise component is adaptively removed according to the noise level. It becomes possible to realize a noise removing circuit which is hardly affected by sudden noise regardless of moving images and still images.

FIG. 2 is a block diagram showing a second embodiment of the present invention. As shown in FIG. 2, this embodiment is
/ D converter 11, 1-frame memory 12, difference circuit 13, synchronization signal generation circuit 14, sampling circuit 1
5, a coefficient generation circuit 16, a Y / C separation circuit 17, and a B
It comprises a PF 18, a ROM 19, a non-linear processing circuit 20, and a subtraction circuit 21. The present invention is an example realized by changing the first noise detection method shown in FIG. 1 to a noise detection method between frames, and a 1-frame memory 12 and a subtraction circuit 13 are provided, and a linear processing circuit of the nonlinear processing circuit 20 is provided. The waveform is selected by the coefficient generation circuit 16.

The video signal 109 is input to the A / D converter 11 and output as a digitized input signal 110. The input signal 110 is input to the 1-frame memory 12, delayed by 1 frame time, that is, 1/30 second, and output as the output signal 11. The difference between the input signal 110 and the output signal 11 is detected by the difference circuit 13, and the difference signal 112 is output. Further, the input signal 110 is input to the sync signal generation circuit 14, and the timing signal 113 (see FIG. 6) of the part where the sync signal does not change, that is, the no-signal part (see FIG. 6) is generated and output while being the sync signal of the vertical sync signal part. To be done. The timing signal 113 causes the sampling circuit 15 to extract the vertical sync non-signal portion from the output signal 111, and the coefficient generation circuit 16
Is output as the noise level value 114. The signal extracted by the sampling circuit 15 should be one frame difference of the non-signal portion and 0 should be output. However, if there is noise, only the noise component is output to the extracted signal. From this, the noise level value 114 represents the noise level, and for example, values such as “1”, “2”, and “3” are output in ascending order of the noise level.

On the other hand, the input signal 110 is input to the Y / C separation circuit 17 which divides the luminance signal and the color signal into the luminance signal 1
15 is output. From the luminance signal 115, the BPF 18 having a peak at 1.7 MHz as shown in FIG.
A high frequency component having a noise component is extracted and input to the nonlinear processing circuit 20. In the ROM 19, two or more patterns of predetermined non-linear waveforms for non-linear processing are stored. The waveform in the ROM 19 is selected as follows according to the value of the noise level value 114. For example, when the noise level value 114 is a luminance signal with little noise such as "1", the non-linear waveform as shown in FIG. 7A is selected to reduce the high frequency component pass band. When the noise level value 114 is an intermediate noise level such as "2", the non-linear waveform used in the conventional technique as shown in FIG. 7B is selected. Further, for a luminance signal having a noise level value of "3", a non-linear waveform that allows more high frequency components of the waveform as shown in FIG. 7C to be selected. The luminance signal 115 is processed by the non-linear processing circuit 20 by these selected waveforms and output as the non-linear processed signal 116. Next, the non-linear processed signal 116 is input to the subtraction circuit 21, and the noise removal output signal 117 is obtained through the subtraction operation with the luminance signal 115. As a result, the luminance signal with less noise is processed while leaving the high frequency component, and the luminance signal with a lot of noise is processed with the high frequency component dropped, so that the noise component can be adaptively removed according to the noise level. Therefore, regardless of whether it is a moving image or a still image, noise removal that is not easily affected by sudden noise can be realized.

[0016]

As described above, according to the present invention, the level of the noise portion in the no-signal portion in the vertical synchronization period is detected, and the noise level is integrated by the integrating circuit. In addition to eliminating the drawback of excessive response due to sudden noise, it also has the drawback of malfunction in the case of moving images in which components other than noise are extracted in the frame difference signal in frame component noise extraction as in the past. Is also eliminated, and the noise of the video signal can be removed according to the noise level.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a block diagram showing another conventional example.

FIG. 5 is a diagram showing characteristics of a bandpass filter.

FIG. 6 is a timing diagram showing a video signal and a timing signal.

FIG. 7 is a diagram showing ROM contents for non-linear processing.

[Explanation of symbols]

 1,11,23,28,29 A / D converter 2,14 Synchronous signal generating circuit 3,15 Sampling circuit 4 Integrating circuit 5,16 Coefficient generating circuit 6,17,27 Y / C separation circuit 7,18 BPF 8 , 19 ROM 9, 20, 35, 36 Non-linear processing circuit 10, 21, 31, 32 Subtraction circuit 12 1 Frame memory 13 Difference circuit 22 Noise detection circuit 24 CPU 25 Video signal processing circuit 26 CRT 30 Y / C mixer 33 Timing Generator 34 Field memory 37 Switch

Claims (2)

[Claims] 1. A for converting a video signal into a digital signal
An A / D converter, a sync signal generation circuit for inputting the digital video signal output from the A / D converter, and extracting and outputting a timing signal of a no-signal portion in the vertical synchronization signal, and the timing signal A sampling circuit for extracting and outputting the noise of the vertical synchronization non-signal portion from the digital video signal through the digital video signal; and an integrating circuit for integrating and outputting the noise of the vertical synchronization non-signal portion extracted by the sampling circuit, A coefficient generation circuit that inputs the integrated signal of noise output from the integration circuit, sets and outputs a noise level value corresponding to the noise, and inputs the digital video signal and separates the luminance signal from the digital video signal. And a luminance signal separating circuit that outputs the luminance signal, and inputs the luminance signal to extract a high frequency component including a noise component in the luminance signal. Corresponding to the noise level value input from the coefficient generation circuit, and a high-frequency component detection circuit that outputs the noise level value, a storage circuit that stores a plurality of patterns of non-linear waveforms that are preset for non-linear processing with respect to the noise level value. A non-linear processing circuit that appropriately selects a non-linear waveform pattern in the storage circuit and performs non-linear processing on a signal including a high frequency component output from the high frequency component detection circuit based on the selected non-linear waveform. A subtraction circuit that subtracts the nonlinear processed signal output from the nonlinear processing circuit from the brightness signal output from the luminance signal separation circuit. 2. A for converting a video signal into a digital signal
A / D converter, a 1-frame memory for inputting a digital video signal output from the A / D converter, delaying the digital video signal by 1 frame and outputting the delayed digital video signal, and a 1-frame memory for the digital video signal. A differential circuit for subtracting the digital video signal output from the A / D converter and a digital video signal output from the A / D converter are input to extract a timing signal of a non-signal portion in the vertical synchronizing signal. A sync signal generating circuit for outputting the noise, and a sampling circuit for extracting and outputting noise of a vertical sync no-signal portion from the difference signal via the timing signal; and a vertical sync no-signal portion extracted by the sampling circuit. A noise generation circuit for inputting the noise of, and setting and outputting a noise level value corresponding to the noise, Luminance signal separating circuit for inputting a video signal and separating and outputting a luminance signal from the digital video signal; and for inputting the luminance signal, extracting a high frequency component including a noise component in the luminance signal. Corresponding to the noise level value input from the coefficient generation circuit, and a high-frequency component detection circuit that outputs the noise level value, a storage circuit that stores a plurality of patterns of non-linear waveforms that are preset for nonlinear processing with respect to the noise level value, A non-linear processing circuit that appropriately selects a non-linear waveform pattern of the storage circuit, and performs non-linear processing on a signal including a high frequency component output from the high frequency component detection circuit according to the selected non-linear waveform; A subtraction circuit for subtracting the non-linear processed signal output from the non-linear processing circuit from the brightness signal output from the brightness signal separation circuit; The noise elimination circuit, characterized in that it also comprises a.